Structure functions of unstable lithium isotopes

Abstract

We study the spin-average and spin-dependent structure functions of the lithium isotopes. It is found that the light-cone momentum distribution of the valence neutron in the halo of 11Li is very sharp and symmetric around y=1, because of the weak binding. This implies that such neutrons are in an environment very close to that of a free neutron. The EMC ratios for Li isotopes are then calculated. Furthermore, we investigate a new ratio, given by the difference between the Li structure functions of mass number A ( F 2 A ) and A−1 ( F 2 A−1 ) divided by the difference between the structure functions of the deuteron and free proton. We study the possibility of extracting the neutron structure function from data for the nuclear structure functions of the Li isotopes. In particular, the ratios for A=9 and 11 present an attractive possibility for extracting the free neutron structure function. Next, as an example, we calculate the spin-dependent structure function of 9Li isotope, which has spin 3/2. The spin structure function is given in terms of the multipole spin structure functions; 3/2 1g 1 , which is analogous to the usual spin structure function, g 1, for a target with spin 1/2, and a new one, 3/2 3g 1 , which first arises for a target with spin 3/2. The effect of the nuclear binding and Fermi motion on 3/2 1g 1 is about 10% in the region x<0.7, but it becomes quite important at large x. The spin structure function, 3/2 3g 1 , is negative at small x but it becomes positive in the region 0.2< x<0.5. However, the magnitude is very small. At large x it is again negative and its absolute value becomes large because of the Fermi motion. Finally, we discuss the modification of the Gottfried and Bjorken integrals in a nuclear medium and point out several candidates for a pair of mirror nuclei to study the flavor-nonsinglet quark distributions in nuclei.